There has long been a market for puzzles and games that are aimed at adults rather than young children. One area of the adult gaming market is 3D-puzzles. This is where the user has to solve a puzzle in 3 dimensions. The most famous of these puzzles is the Rubik's cube. This puzzle was invented in 1974 by Erno Rubik and challenges the user to align the segments of the cube so that each side is a homogenous color. This puzzle became a worldwide phenomenon in the 1980s and 100 million pieces were sold in the period 1980-82. Many other similar puzzles were introduced to cash-in on this market.
An example of a more recent puzzle is the 3D-pyramid. Like the Rubik's cube the aim of this puzzle is to arrange the segments in three dimensions so that all sides are a different homogeneous color. Unlike the Rubik's cube each segment is detachable and coupled to the neighboring segments via plastic slip connectors.
These puzzles can be fun for the user but if the desired end state cannot be reached, and there is no prospect of doing this, then interest is often lost and the puzzle is discarded. Conversely, if the puzzle is too easy then the user solves the puzzle and it is also discarded. Both of these scenarios can be assigned to the fact that the segments have fixed colors giving the puzzle only one difficulty level.